The present invention relates to a gripping arrangement. More particularly, it relates to a arrangement for manipulators, particularly industrial robots, but also can be used in other technical fields and for example also in tool exchanges devices of numerically controlled working units, especially horizontal working centers.
Gripping arrangements of the above-mentioned general type for tool exchange devices are known, in which gripping fingers are arranged at both ends in a housing. They are formed so that in the gripping position outwardly of the housing to grip an object, for example a tool, the object is received and held in their mouth-like open gripping ends. The gripping fingers are held and guided in the housing so that their gripping ends project outwardly beyond the housing only in the gripping position, whereas in their inoperative position for releasing the object they are retracted at least substantially completely and without projecting outwardly, inside the housing. Both gripping fingers are translatorily reciprocable along guiding paths in the housing. They are extended or retracted with the aid of a toothed rod guided in the housing by a rotary drive of a pin engaging with the toothed rod. Both gripping fingers are coupled hingedly and spring-loaded. One of the gripping fingers can turn at the end of the housing opening to the mouth-like open position. The guiding paths along which the gripping fingers reciprocate are rectilinear, and always only one gripping finger is translatorily reciprocable and forms a fixed part of a rectilinear rod provided with the toothed rod and linearly displaceable by the pinion. The other gripping finger is turnably moveable on the first-mentioned gripping finger and displaceable together with the latter during its linear displacement.
In another construction, namely for a sorting star for bottle sorting installations, arcuate fingers with arc-shaped closing movement and formed as so-called blocking fingers are known. They form additional components of a bottle receptacle and operate so that by the arcuate extension the bottle received inside the bottle receptacle is secured at its rear end from falling out in the manner that the extended arcuate finger closes the bottle receptacle at the rear end of the bottle supported therein.
The known arrangements of the above-described type have the disadvantage that the gripping fingers during turning movement from the releasing position to the gripping position and vice versa pass through a great radial region neighboring to the rotary object to be engaged. For a disturbance-free movement course a sufficient free place for the object to be gripped must be available in this radial neighboring region. When this is not provided, there will be a danger of collision. At the same time the known gripping arrangements require great neighboring free space. They cannot be used in conditions of narrow working places and when such free spaces are not available. Moreover, the movement course requires running over a relatively great path. Thereby a very high idle time takes place. The gripping process and in some cases a subsequent exchange process are thereby relatively long, and in any case is not as fast as desirable. Moreover, the known gripping arrangements are voluminous, heavy, complicated in construction and function and also expensive. Especially in the situations when a relatively larger and heavy object is to be gripped, the known gripping arrangements must be designed very strong and bending-resistant. Since further it must be guaranteed that in the gripping position both gripping fingers of the engaged object are held reliable, considerable holding forces must be provided in the gripping position to prevent falling out. Especially when in the gripping position the gripping arrangement moves with high speed from one position to the other, for example in tool exchange devices for numerically controlled power tools, when high centrifugal forces act on the gripped objects, the holding forces must be especially high. This requires a provision of powerful, voluminous and heavy as well as expensive driving devices for the gripping fingers.